Steam Problems



Hi Guys,
I may be being a bit thick asking this, but i've installed steam, I'm
running Vista RC1, and all I get come up when I try to play cs or hl2 is
'game currently unavailabe, please try again later'???
My system is:-
2Gb Memory,
3Ghz Intel p4 ht,
512MB Nvidia 6800Ultra,
Hardware's capable of running no problem.
Am I missing something obvious? I've seen loads of posts with no problems
running it?
I'd really like some help here, as I'm thinking of reverting back to XP Pro
to play them.
Thanks all....

My Computer